1-3 NL 1010 low board
 

I was playing at a 1-3 game last night. I've been playing TAG and avoiding marginal situations and villian knows this. Villian is playing well and i've seen him make some tricky plays already. He was up to about 600 but ran into some cold cards.

Hero ~$300
Villian~$400

Folds to UTG+2 who raises to $10, villian calls, hero raises to $25 in cutoff with 1010. Blinds Fold, UTG+2folds, villian calls.

pot=$64

Flop 3c 5d 7d

Villian checks, Hero bets $40, villian tanks and then calls

pot=$144

Turn 6s

Villian bets $50, hero tanks and calls

pot=$244

river 2s

villian bets $75, hero?

I really don't think he has a pair higher than tens but the only hand i beat is a busted flush or some other bluff. I think i should fold on the turn but it was live and i had a feeling he was weak. It feels like he's playing this like a set or pocket 4's but i know that he knows i have an overpair and i feel like he's capable of bluffing here.
-Was the flop bet the right amount?
-Should i have folded the turn?
-Do i have to call the river after calling the turn?